This invention relates to a stamped knitting tool, particularly for knitting and warp knitting machines having a carrier provided with at least one guide groove for reciprocating knitting tools and also relates to a knitting or warp knitting machine.
The knitting tool is of the type which has a shank provided with at least one butt and which has a guide region extending along at least one part of the shank length and which is at all times situated in the guide groove when the knitting tool is positioned therein. By knitting tools latch needles, hook needles, sinkers, or similar components are meant which are used for forming loops in a great variety of textile machines.
For example, circular knitting machines work with a needle cylinder which has axially parallel guide grooves separated from one another by guide webs and guiding back-and-forth shiftable latch needles therein. The needle cylinder is surrounded by a cylinder cam having at least one cam channel into which extends a butt which forms part of each individual latch needle and which projects radially beyond the guide webs of the needle cylinder. By virtue of a relative displacement between the needle cylinder and the cylinder cam, the required reciprocating motion of the latch needles in the guide grooves of the needle cylinder is conventionally generated. Basically the same considerations apply for a dial which, as a rule, is associated with the needle cylinder and which, dependent upon the type of the knitting machine, is also provided with latch needles or sinkers and with which a (dial cam) is associated.
During their reciprocating motion in the respective guide grooves, the latch needles or sinkers lie, with their narrow edge, on the bottom of the guide grooves while, at the same time, they are supported on their broad opposite faces by the laterally bounding guide webs on either side of the respective guide groove. Frequently, the shank of the latch needles has a "spring bend", that is, the shank is slightly bent (kinked) laterally about a line which is perpendicular to the shank axis. As a result, the shank, at least in its region oriented towards the needle hook, is maintained resiliently pressed against a guide web and thus may be guided without any lateral play.
With the increase of the knitting speed in current machines made possible by the latest needle and cam structures (for example, a needle cylinder rpm of over 28 for a needle cylinder diameter of 30 inches), the heat generated by the motion of the needle in the guide grooves has become increasingly significant. As a result of such a heat, the needle cylinder or the dial, as well as the heat-conducting components structurally connected therewith, attain an operating temperature in the order of magnitude of 80.degree. C. and above during an extended operation. Such high operating temperatures cause mostly local, non-uniform dimensional changes of cooperating parts moving relative to one another. Thus, as a consequence, components of narrow tolerances such as guide webs, needles, cam parts and the like are exposed to an increased wear or may even mutually jam. Furthermore, the energy input for the machine drive increases to an undesired extent.
Viewed overall, such an increase in the operating temperature frequently has a limiting effect on a further increase of the operational rpm of the machine. Since the output of a circular knitting machine depends directly from its rpm, the efficiency of the machine is thereby also limited.
To remedy the above-outlined drawback, it has been attempted to improve the lubricating conditions for the knitting tools in the guide grooves to thus reduce the friction which appears during the reciprocating motion of the tool. Thus, for example, the needle shank of latch needles has been provided with longitudinally extending grooves which are oriented parallel to the needle back and are provided on at least one broad side of the shank as described in German Offenlegungsschrift (application published without examination) 36 12 316, to which correspond U.S. Pat. Nos. 4,625,527 and 4,681,150. Apart from a desired reduction of the inert mass of the needle by taking into account a reduction of the forces and jarring effects during acceleration and deceleration of the needle, an improved lubricant distribution over the guiding length of the shank needle has been sought to be achieved. Similar purposes are served by the construction of a needle shank described in Japanese Patent publication 5-195395 where the shank of a latch needle has, in the region between the needle head and the butt, at least one bridge which is disposed higher than the needle head. In the needle shank portion which couples the needle butt with the bridge, a depression is provided into which, during operation, lubricating oil is introduced by an oil supply device disposed in the cam jacket. The oil quantity which dwells in the depression is sought to provide a more effective lubricant distribution over the length of the guide region of the needle shank in the guide groove during a reciprocating motion of the latch needle and is further sought to result in an improved lubrication in the region of the butt proper.
Another approach for reducing the motion resistance in reciprocating knitting tools by improving lubrication is described in German Patent No. 196 04 954. In the stamped knitting tool (for example, a hook needle or a latch needle) described therein, the needle shank is at least on one of its two opposite broad side faces provided with lubricant distributing means having at least one region which is of reduced shank thickness and which is shaped as a chamfer or a recess oriented transversely to the longitudinal direction of the shank. Such a chamfer or recess extends from a location which is at a distance from the upper shank edge until or almost until the lower shank edge. In an alternative embodiment the lubricant distributing means provided at least on one of the two broad sides of the needle shank has at least in one region a reduced shank thickness formed as a depression which extends transversely to the longitudinal dimension of the shank and which further extends to or close to the lower shank edge. The depression has a substantially wedge-shaped or dish-shaped cross-sectional configuration. The width of such a depression, as viewed parallel to the length dimension of the needle shank, is, however, limited in achieving the intended purpose.
The above-noted measures for improving the lubricant distribution in guide grooves are generally effective. They do not, however, allow an increase of the operational rpm of circular knitting machines beyond a certain limit. Also, lubricant cannot be introduced in a desired quantity into the guide channels of the needle cylinder or the dial, because of the risk that the lubricant gains access to the fabric and soils the same, necessitating a subsequent cleaning of the fabric or other treatment which is an added expense and which in some instances cannot even be performed.